The invention relates to xerographic or electrostatic copying apparatuses of the type which produce copies from an original whose image consists of lines of print, paragraphs, or other such sections. More specifically, the invention relates to copying apparatuses of the type capable of producing a copy of only selected lines, paragraphs or other such sections of the original. Typically, such copying apparatuses are comprised of a transparent support surface onto which the original is laid face down. The original is illuminated, and light from the original is projected onto an electrostatically charged light-sensitive surface to effect image-dependent discharge of the surface, and accordingly produce an electrostatic image of the original. The electrostatic image is developed to form a visible image. Possibly also, the visible image on the light-sensitive surface is then transferred onto copy material, and the image on the copy material is then fixed.
A known rotary duplicator machine of the type in question is capable of copying only selected portions of the text on an original to be copied. The original is scanned by scanning light and the light from the scanned original is projected onto an electrostatically charged semiconductor surface. The resulting electrostatic image is thereupon developed in preparation for printing. The illumination of the original and the projection of image light upon the semiconductor surface proceed in a line-by-line manner. After light corresponding to one line of the original has been projected onto a corresponding strip of the charged surface, the copying drum is indexed a distance corresponding to one line, whereupon the projection of image light from the next line to be copied from the original occurs. The requisite step-by-step advancement of the semiconductor surface and the corresponding step-by-step exposure operation involves considerable expense for the necessary mechanisms and control circuitry. It is very difficult to incorporate such means into existing copying apparatuses or copying apparatus designs. Additionally, this prior-art expedient greatly slows down the rate at which copying can proceed. Also, the known expedient involves a troublesome rotary return movement of the semi-conductor surface.